Elevators having elevator car are type of transportation where the elevator car travels vertically or approximately vertically to a landing within a hoistway. The elevator car is typically travelling upon car guide rails and serves stations, landing or floors along way of the car vertical travelling.
Automatic elevators are referred to as elevator cars that respond automatically by momentary pressing a button that calls the elevator car to a designated floor and without stopping between floors.
Non automatic elevators are referred to as elevators that the button that calls the elevator car to the designated stop must be pressed until the elevator car reaches to the designated floor.
A conventional elevator typically includes, elevator control panel, elevator car which is used to lift and lowering a load such as but not limited to people. The elevator car is designed to lift predetermine maximum load. A counterweight is used for balancing the elevator car, usually the counterweight weights 50% from the maximum allowed weight in the elevator car. The elevator further includes cables or ropes that are connected between the counterweight and the elevator car. The elevator further includes a lifting machine that is used as a driving force for lifting and lowering the elevator car load. The elevator car further includes a safety braking or catching mechanism such as but not limited to guide rail braking safety system which is a mechanical catching device that is used to break or lock the elevator car on the elevator guide rails, for example in case where there is a free falling of the elevator car. The mechanical catching device can be operated mechanically or operated by an electrical command.
The lifting mechanism typically includes an electric motor which is used for driving directly or with transmission arrangement of friction wheels. Upon the friction wheels hanged the cables that are connected between the elevator car and the counterweight. The friction between the cables and the friction wheels allows travel movement of the elevator car and the counterweight which are driving by the lifting machine. The elevator further includes a flywheel or any other means that is typically connected directly or indirectly to the electric motor shaft which helps to stop/brake the lifting machine. On the lifting machine typically installed one or more braking(s) devices that are used to prevent from the lifting machine travelling of the elevator car when the electric motor of the lifting machine doesn't receive electrical current. The braking(s) device(s) and the electrical motor receive electric power from the same source. When the braking(s) device(s) receives electric power they are held open electrically allowing the motor rotation. A power failure will cause the brake to engage with the flywheel and prevent the elevator from moving. The braking(s) device(s) typically include one or more shoes or pad drop. The braking(s) device(s) further includes one or more adjustable braking springs and one or more electromagnets. When the electric motor receives electric power, this brake is electrically lifted or “picked” against the adjustable tensioned or compressed springs. When the electric motor doesn't receives electric power the electrical power is also removed from the braking(s) device(s), these springs ensure the immediately drops back against the flyingwheel, bringing the car to a safe stop. When the braking(s) device(s) are not energized they will securely hold in place the elevator and the counterweight. When the elevator car travelling movement is desired the electromagnet is energized thereby a force is applied on the shoes or pads causing them to depart slightly from the flywheel and thus the flywheel can rotate freely. Some of the braking devices include adjusting means such as an adjusting screw that is used for adjusting the distance between the brake shoes and the flywheel and also for adjusting the pressure that brake spring(s) apply on the flywheel when the electromagnet is not energized.
The braking force is determined according to the weight of the elevator because the counterweight is heavier than the weight of the elevator car and the weight is roughly equal to the weight of the elevator car with approximately half of the load permitted to carry in the elevator car due to an imbalance between the elevator car weight and the counterweight. The brake is considered a safety device that without the braking device the elevator car will move freely due to the imbalance between the elevator car weight and the counterweight.
During normal working hours of the elevator there is a friction reduction, the brake shoes are worn away and the braking force of the brakes is reduced. This friction reduction of the brake shoes is reduced even more as a result of an electrical fault. In this case the brake shoes are not open when the motor receives voltage and manages to rotate the flywheel even when the brake shoes are in a closed position. Another known fault is when the braking shoes remains open even though the electromagnet is not receiving voltage. In each of these cases described above, the elevator car will move freely and without control, even when the elevator car doors and hoistway doors are open.
In such cases, the elevator control panel does not receives electrical signals that notifies that the elevator car is moving in the hoistway and therefore will not do anything to prevent this action. What is needed in this scenario is activation of the emergency brake that locks for example the elevator car on the elevator guide rails and prevents elevator car movement.
U.S. Pat. No. 5,509,505 describes an arrangement for detecting elevator car position relative to a floor landing includes an optical potentiometer associated with both the elevator car and the interior of an elevator hoistway. One portion of the potentiometer is attached to the elevator car, while the other portion of the potentiometer is fixed within the hoistway. Car position is ascertained by illuminating portions of a fluorescent fiber optical cable and then reading electrical signals outputted by photodetectors at either end of the cable. The difference between the electrical signals corresponds to the distance of the elevator car from the landing.
U.S. Pat. No. 3,685,618 describes a floor selector comprising a tracing means moved with the elevator movement, but on a reduced scale, and a preceding means driven ahead of the tracing means simultaneously with start of the elevator cage at a higher speed than the tracing means; wherein molded oscillators are installed on the tracing means, molded receivers are provided on the preceding means, and the outputs of the receiver are combined logically whereby various signals for controlling the elevator operation are obtained.
US 20130025973A1 describe An elevator control device includes a control device body controlling operation of one or more elevators operated between plural floors of a building, and carries out emergency evacuation operation for evacuating people by using an elevator when the building suffers from fire, earthquake, or the like. The elevator control device includes a damage detector that detects damage due to disaster at each floor and outputs the detected damage as damage information of each floor; and a person detector that detects the number and positions of persons present at each floor and outputs these data as person number and position information, and in the emergency evacuation operation, the elevator control device body develops an elevator evacuation operation plan based on the position of the elevator car, the damage information, and the person number and position information, and controls the operation of elevator based on the developed evacuation operation plan.
U.S. Pat. No. 4,245,721 describe a U-shaped channel is mounted on the elevator car. A solid vane is mounted on the shaft wall near each floor. As the car approaches each floor the vane passes between the walls of the U-shaped column. A plurality of photo transmitter-receivers are mounted on the channel. The receivers on one wall and the transmitters on the opposite wall. As the vane passes between the walls, it obscures or occludes the light from the transmitters and the receivers are successively turned on and off in an arrangement indicative of the distance to the floor level.
U.S. Pat. No. 8,584,812 describes a brake monitor for monitoring a brake system of an elevator system that includes a drive and a drive controller checks for a travel signal generated by the elevator system. If a brake-release signal is not received within a time-window after the occurrence of the travel signal, the brake monitor activates a relay circuit for interrupting a safety circuit of the elevator system or for interrupting a control voltage of the drive controller so that the elevator system can be stopped.
CA2731667C describe brake monitor for monitoring a brake system of an elevator system that includes a drive and a drive controller in addition to the brake system. The brake monitor includes a first brake signal input for electrically connecting the brake monitor to a first brake contact of the brake system. The brake monitor further comprises a driving signal input for connecting the brake monitor to a first electrical driving signal line of the drive controller. Also provided are a power supply, a microprocessor and a relay circuit. The relay circuit is configured such that it can be activated for interrupting a safety circuit of the elevator system or for interrupting a control voltage of the drive controller so that the elevator system can be stopped.
US2011011682 describes an elevator drive has a brake device with compression springs to actuate brake levers, and brake linings on a brake drum creating a braking force. A sensor is provided to detect the movement of a brake magnet armature tappet. A bracket is attached to the brake magnet tappet on one end and a distance piece carrying the sensor housing is arranged on the other end. A restoring lug is attached to the existing mechanical indicator. A monitor evaluates the sensor signal and turns off the elevator drive in the event of dangerous operational states via a safety circuit. The system allows the state of the brake device to be monitored. The more the brake linings wear off due to abrasion, the smaller the distance between the armature and the brake magnet housing. If the armature is in contact with the brake magnet housing, the braking ability of the brake linings is completely void.
The problem with this solutions is that normally with existing elevators there are many types of elevator motors and brakes, thus there is a need to match for each motor and brake the right sensitive electric switches and sensors that will fit and there is a need to customize the way the switches are connected or grabbed with the motor/brake.
In addition every type of elevator typically have different control panel and when installing additional switches for monitoring the brakes there is a need to do changes in the elevator control panel. Changes in the elevator control panel require authority's approval. In addition the installation time of the sensitive switches is long and expensive.
Furthermore, the efficiency of such a switches system is not very high, first, it requires very sensitive switches with a small crawl space of about 1 mm which are installed in an unclean environment and therefore their reliability over the years is reduced. An additional disadvantage of the methods known in the art is that it checks if the brake does not open or the does not close which is based on the state of the switches. In this method the elevator system cannot recognize for example the state of the brake shoes and the grade erosion of the brake shoes that may cause the elevator car moving freely when the electric motor doesn't receive power. In this case, the switches system shows that brake shoes are in closed state while elevator car moving freely because there isn't friction or small friction between the flywheel and the brake shoes.
The solutions which are known in the art are, monitoring the status of the brakes by adding one or more switches which are sensitive on the brake shoes that change their state according to a gap between the flywheel and the brake shoes. If for some reason the brake is not open when the electric motor receives electric power or the brake is not in closed position when the electric motor doesn't receive electric power, the control panel of the elevator will stop the power to the electric motor.
One of the objects of the present invention is to provide elevator brake monitoring system and method that monitor also the erosion of the brake shoes.
Yet another object of the present invention is to provide elevator brake monitoring system and method that monitor the erosion of the brake shoes which is not dependent with the switching system that was described above.
Yet another object of the present invention is to provide elevator brake monitoring system and method which is based on monitoring of the state of the electric power to the brake(s) and the elevator car position. By these monitoring, a decision is made to decide if whether to activate the elevator emergency brake or not.
Another object of the present invention is to provide elevator brake monitoring/controlling system and method which is simple to install and use and can fit for all types of elevators that moves with cables/ropes and lifting machine is equipped with brake(s).
Another object of the present invention is to ensure that the emergency brake will not be activated whenever the car stops between floors intentionally or unintentionally during normal operation.